It is known to use a vacuum dump valve comprising a spring loaded plunger that normally seals a vacuum line but which vents the line to atmosphere upon movement of the plunger. Such valves are used, for example, to sense depression of an automobile's brake pedal. In operation, the dump valve seals the speed control vacuum system when the brake pedal is the normal nondepressed condition and opens the vacuum system upon depression of the brake pedal to deenergize the auto's speed control system.
More specifically, known valves consist of a housing, plunger, O-ring, spring and washer. Assembly is accomplished by first inserting the plunger/O-ring/spring assembly into the housing and closing the housing with a metal washer which allows the end of the plunger to extend therethrough. The washer functions as a retainer and plunger guide. Washer retention is effected by preheating a plastic shoulder on the housing, positioning the washer, and reforming the softened plastic around the washer. The aforesaid construction and method of manufacture has caused problems in that the valve is process dependent. For example, irregularities in the plastic deformation necessary to retain the washer have been responsible for variations in valve performance.